Power supply system of an electronic switching electric motor for air-conditioning devices to be installed inside the motor vehicles

ABSTRACT

A power supply system of an electronic switching electric motor for air-conditioning devices is described, said power supply system is intended to be installed in the motor vehicles and comprises a solar panel ( 13 ), which is an integral part of the vehicle and supplies electric energy to the motor ( 4, 52 ). The electric motor ( 4, 52 ) can be further powered by the vehicle battery ( 54 ), in a way that no specific equipment is needed to convert the energy, nor converting devices are needed between the motor ( 4, 52 ) and the solar panel ( 13 ). Solar panels ( 13 ) can be used with a higher voltage output than that of the vehicle battery, in such a way as to draw the available electric energy at a voltage and current level suitable to achieve a significant decrease of the dissipation of energy in the system, with the same sections of wiring or in accordance with the known techniques of the low voltage solar panels.

TECHNICAL FIELD

The present invention refers to an electronic switching power supplysystem for air-conditioning devices to be installed inside motorvehicles.

BACKGROUND

The air-cooling of the vehicle passenger compartment, when the vehicleis parked, is greatly limited by the lack of an autonomous source thatsupplies electric energy when the engine is switched off.

In fact, the amount of electric energy supplied by the storage batteryalready present in the vehicle is insufficient to guarantee suchair-cooling for a prolonged period of time.

On the other hand, it would be extremely useful to implement such asystem in the motorcars, in order to obtain undoubted advantages interms of comfort for the user of the vehicle; furthermore, the existingair-conditioning system in the vehicle could be made even moreefficient, with respect to the known art, by minimizing the amount ofheat to dispose of at the ignition of the engine.

The installation of a photovoltaic cell on the roof of the vehicle, inthe form of a solar panel, partially enables the difficulties mentionedabove to be overcome, since the fan of the air-conditioning device ispowered by the energy supplied by the solar panels.

However, since, for economic reasons, the same electric motor of the fanis used, and said fan is also powered by the storage battery of thevehicle, it is necessary to interpose at least one energy device adapterbetween the motor and the solar panel, in such a way as to use theavailable electric energy efficiently, allowing for the fact thatoscillations of available power are produced, caused by the variationsof the sun radiation and of the temperature of the panel.

FIG. 1 shows a Cartesian drawing of the V-I characteristics of a solarpanel for traditional motorcar use, wherein, on the axis of abscissas,the voltage values (V) are indicated in Volt and, on the axis ofordinates, the current intensity values (I) are indicated in Ampere.

It is evident that such a solar panel is similar to a current generatorsubstantially up to the axis indicated by A, i.e. just next to theknee-point of the curves, which are shown in the Cartesian diagram ofFIG. 1.

In said FIG. 1, there is a point in the characteristic curve, indicatedby the letter G, equal to a radiation flow of 700 W/m² and to atemperature of about 25 degrees centigrade, wherein the panel has itsmaximum energy efficiency.

The locus of the points of maximum energy efficiency, that is given bythe product of the output voltage with the output current, when theradiant incident power changes, is, by good approximation, a verticalstraight line (isovoltage, indicated by the letter X in FIG. 1), while,by changing the temperature, the locus of the points of maximum energyefficiency is a horizontal straight line (isocurrent).

Further, in the Cartesian diagram of FIG. 1, a point of maximumefficiency at the temperature of 65° C. is indicated with the letter H.

It can be demonstrated that the efficiency decreases by about 0.5% pereach Kelvin grade.

Allowing that the direct current electric machines with a commutator areoptimised to function to a given supply voltage, when the power supplyis an element with an elevated dynamic impedance, such as a currentgenerator, as in the case of a solar panel, the panel-motor systemfunctions in low efficiency conditions, which are worsened in conditionsof low sun irradiation.

To overcome this inconvenience, a direct current converter is interposedbetween the solar panel and the motor, as shown in FIG. 2, wherein ablock corresponding to the solar panel is indicated by number 13, ablock corresponding to the motor by number 4, and a block correspondingto the direct current converter by number 2.

A power output control device , indicated by the number 3 in FIG. 2, canbe interfaced with the wiring of the vehicle, which is indicatedgenerally by 6.

Such embodiments were necessary, to improve the energy match, however,this type of solution is expensive in economic terms and in terms ofoverall size and weight.

Furthermore, it is necessary to consider, in the global energy balance,the conversion losses inevitably introduced by the direct currentconverter 2.

Finally, to work the system at the maximum efficiency point, it isnecessary to provide a temperature sensor on panel 13, which inevitably,increases the production costs.

In conclusion, if the converter 2 is fitted in the proximity of thesolar panel 13, as is usually done in motorcars, an elevated value ofcurrent intensity passes through the wiring resistance 5, therebylowering the system efficiency.

SUMMARY

A purpose of the present invention is to overcome the above mentionedinconveniences, and to provide a power supply system of an electronicswitching electric motor for air-conditioning devices to be installedinside the vehicles. In order to have the maximum use of the availableenergy at the output terminals of the solar panel to power the motor,the system may be configured without interposing any electronicconversion or electronic control device between the two objects.

Another purpose of this invention is to realise a power supply system ofan electronic switching electric motor, without using expensivecomponents or complex technologies.

Such objectives are achieved by a power supply system of an electronicswitching electric motor for air-conditioning devices to be installedinside the motor vehicles made in accordance with the present inventionas disclosed herein.

Using the operating characteristics of an electronic switching motorwith a double machine, that uses, in its electronic control unit, amicroprocessor and a very low friction method of rotor suspension, it ispossible to obtain the power supply system as claimed in claim 1, usingthe aforesaid electronic switching motor in two different operatingmodes, one relative to the system powered by the storage battery and bythe traditional electric system found in motor vehicles, the otherrelative to a power generated by a solar panel.

The switching between the two operating modes is automatic and it doesnot require any additional components nor signals from an externalsource, as it uses an electromagnetic relay that is already present inthe traditional type of an electronic switching motor.

DESCRIPTION OF THE DRAWINGS

The characteristics and the advantages of the present invention will bemade clear in the following description, using non-limiting examples,and by referring to the attached figures, in which:

FIG. 1 shows a Cartesian diagram that illustrates the voltage-currentcharacteristics of a solar panel for motorcars of a known type;

FIG. 2 illustrates a block diagram of a power supply system for electricbrush motors and commutator with adapter converter for traditional typeair-conditioning devices;

FIG. 3 shows a general block diagram of an electronic switching electricmotor power supply system to be installed inside motor vehicleair-conditioning devices, in accordance with the present invention;

FIG. 4 represents a general block diagram of an electronic switchingmotor powered by a power supply system, in accordance with the presentinvention;

FIG. 5 shows a block diagram of an alternative embodiment of anelectronic switching electric motor power supply, to be installed inmotor vehicle air-conditioning devices, in accordance with the presentinvention;

FIG. 6 shows a schematic electronic circuit of a further embodiment ofthe electronic switching electric motor power supply, in accordance withthe present invention.

DETAILED DESCRIPTION

Referring to the figures mentioned above, a solar panel to be installedinside the power supply system. is indicated schematically by number 13.In accordance with the present invention, a direct current converter, ofthe “DC-DC” type used to improve power matching, is indicated by number2, a power control electric device is indicated by number 3, anelectronic switching electric motor is indicated by number 4, the powerwiring of the motor vehicle is indicated by number 5, the control wiringis indicated by number 6, and a temperature sensor to be applied to thesolar panel 13 is indicated by number 7.

With particular reference to FIG. 4, which shows the basic diagram of anelectronic switching electric motor 4 with a double machine, the workingscheme of the power supply system, in accordance with this invention, isas follows.

At the opening of the electric contact which can be activated by theignition lock key or by sending a correct equivalent signal 10, therelay K1, contained in the motor 4, is released by the electroniccontrol unit 12 and the powering of the motor 4, through a quiescentcontact of the relay K1, is secured by a solar panel, indicated by 13,on the electrical conductor 3.

The relay K1 comprises, preferably, an electromechanical or electronicchangeover switch, with a quiescent contact wired to the solar panel 13and an excitation contact wired to the battery 54 of the vehicleelectric system in such a way that, without other control, the motor 4automatically presets to an operating mode using the solar panel 13power, without needing to use signals or power exchanges within the restof the motor vehicle electric system.

The changeover relay k1, integrated in the structure of the electricmotor 4 and not purposely added to achieve the purposes of the presentinvention, is further used to protect the solar panel 13 from theapplication of the inverse voltage of battery 54, when battery 54 powersthe above mentioned electric motor 4.

In the case where the irradiation conditions are suitable, amicroprocessor of the control unit 12 recognises the serviceability ofthe solar panel 13, on the basis of the voltage value present onconductor 41, when relay k1 is released.

Otherwise, if the abovesaid voltage value is not sufficient, the resetcircuit 14 of the microprocessor maintains the circuit in a restcondition until the supply voltage has reached a value for the system tofunction appropriately.

The circuit 14 also provides power to the electronic

The voltage available at the terminals of the solar panel 13 is applied,through the coils L1 and L3 of the motor 4, on the capacitor C1,necessary for the motor 4 to work, thereby providing power to the highvoltage machine 22. The machine 22, since it is positioned downstream a“step-up” converter, has a current generator as its power supply. Thegenerator is represented, in a normal mode, by the coils L2 and L3 inswitching mode and by the diodes D3 and D4 and, in the case where themicroprocessor of the control unit 12 detects the presence of the solarpanel 13, by the solar panel itself.

It should also be noted that the diodes D3 and D4 are structuralcomponents of the electric motor 4 power supply system and that they arenot elements added on purpose to achieve the purposes of the presentinvention; however, they can be used, in this case, to protect the solarpanel 13 from the inverse voltage phenomenon induced by the rotation ofmotor 4 caused by aerodynamic or inertial effects when the solar panel13 works as the electric power supplier in conditions of lowillumination.

The working control of the machine 22 takes place through themicroprocessor that drives, in pulse-width modulation (“PWM”), the“mosfet” transistors TR2 and TR4 and stabilises the voltage on thecapacitor Cl to an optimal efficiency value for the solar panel 13 beingused.

The voltage stabilisation is achieved by modifying the “duty cycle”value of the signal modulated in “PWM” mode.

In this situation, the electric motor 4 works under isovoltageconditions, i.e. the voltage-current characteristic of the solar panel13 moves along the locus of the maximum efficiency points, as the sunirradiation intensity changes.

The low static torque characteristic of this type of motor 4 enables themotor to start even with very low levels of sun irradiation.

In any case, if motor 4 does not start, because it is naturallypositioned on a zero torque point, the microprocessor can control anoperation of rotor positioning, by operating the “mosfet” transistorsTR1 and TR3 of the machine 111.

To allow for variations in efficiency of the solar panel 13 due Sotemperatures, creating very long time constants, an application programcontained in the microprocessor of control unit 12 controls periodicallysmall variations of the “duty-cycle” around the working points,verifying how these variations have an effect on the rotational speed ofthe motor 4.

In fact, the measurement of the rotational speed is a function normallycarried out by the microprocessor for the control of the correctoperation of motor 4 and, if an increase of the rotational condition isverified, the application program will consider this new point as aproper working point; in the opposite case, it will maintain unchangedthe previous working point.

The application program of the control microprocessor is designed, infact, if such a way as to enable operation with just the high voltagemachine 22. The components of said machine comprise the “mosfet”transistors TR2 and TR4 and the inductors L2 and L4, and said machineoptimises the power matching with solar panel 13.

In this way, it is possible to cover the entire characteristic of thesolar panel 13, using its full capacity, thanks to the modification tothe working point under isocurrent conditions.

It should be noted that, when the microprocessor recognizes the presenceof the solar panel 13, no signals are exchanged with the traditionalelectric system of the vehicle, thus guarantying the operating functionsof the electric motor 4 and null or negligible current drain by thepower supply 54 of the motor vehicle, which usually comprises a storagebattery.

Further, it should be noted that the automatic switching in the presenceof the solar panel 13 requires the motor 4 to support a lifetime cornparable to that of a motor vehicle, equal to about 30,000 working hours.

An embodiment of the brushless electric motor 4, 52 with a highreliability rotor support is the best technical and economical solutionthat achieves the predefined lifetime goal.

It is possible, if the available voltage at the solar panel 13 terminalsis low, to interpose a power supply 51 of the “step-up” type between thesolar panel itself 13 or the storage battery 54 and a commutator motor52 designed to function at high voltage, for example 60 Volts, and witha further electronic control unit 53, suitable to adjust the functionsthereof.

FIG. 5 shows the application block diagram of such a system, wherein therelay K1 is emphasized. The relay can switch between two differentoperating modes corresponding to the normal operating mode and to theoperating mode with solar panel 13.

A further electronic control circuit 55 is driven by the motor vehicleand properly adjusts the power supply “step-up” 51 that works as avoltage booster, to match the storage battery voltage 54. The circuit 55is connected to the conductor 411, with the rated operating voltage ofthe motor at a high voltage 52.

In the case where it is desirable to direct the solar panel 13 energytowards a load element 60 rather than the motor 52, the electroniccontrol unit 53 of the motor 52 disconnects the motor, by operating theswitch I, which can be an electromagnetic relay or an electronic switch.Through the electronic circuit control 55, it is possible to produceenergy from the solar panel 13 at the desired voltage value, to anexternal load 60, that is, for example, the storage battery 54 of thevehicle, which, in this case, would be kept charged even when the motorvehicle engine is shut off.

Further, the same result can be achieved using the existing circuitryinside a “brushless” type motor, just by adding switch I.

A circuit application is shown in FIG. 6, wherein it is emphasised thatthe machine 22 is switched off and is not used. The two mosfettransistors TRI and TR3 are driven in parallel, through a pulse-widthmodulation control (“PWM”), operated by means of already existingelectronic components on motor 52 (L1, L3, D3, D4, C1, C2,microprocessor of the control unit 12) as a step-up power supply thatpowers an external load 60, through an electromechanical or electronicswitch I properly controlled by the control logic unit of the controlunit 12.

The load 60, also shown in his embodiment, could be the motor vehiclestorage battery 54.

The microprocessor of the control unit 12 optimises the energyconversion by measuring the voltage at the capacitor terminals C2,thereby making the solar panel 13 work at a point of maximum efficiency.

It is important to underline that the capacitors C1 and C2 and theresultant inductance of machine 112 are structural components of a powersupply system of an electronic switching electric motor and that theyare not elements added especially for to this invention.

Furthermore, they can be used as an electromagnetic filter “EMI” for theprotection of the motor vehicle electric system from problems caused bythe “brushless” type working motor 52. Note again that, if it isnecessary to supply stabilised power to other loads 60, which have anoperating voltage lower than the solar panel output voltage, this,again, can be carried through relay I and the machine 22 will providestabilisation while operating as a “shunt” parallel linear regulator.

From the above description, the characteristics, as well as theadvantages, of a power supply system of an electronic switching electricmotor to be installed in motor vehicle air-conditioning devices areclear.

In particular they are represented by:

possibility to power a ventilator fan of a motor vehicleair-conditioning unit by the motor vehicle battery or by a solar panel,as an integral part of the vehicle, without the need to interpose anyexternal element to the motor for the conversion of energy or for theelectric matching between the motor and the solar panel;

possibility to use solar panels at a high voltage, collecting availableelectric energy at a high voltage and at a low current to allow, withequal sections of wiring, the minimum energy dissipation therein;

possibility to protect the motor vehicle electric system from problemscaused by the working motor;

possibility to protect the solar panel from application of batteryinverse voltage during the operation of the system;

possibility to protect the solar panel from inverse voltage caused bythe motor rotation because of aerodynamic or inertial effects, when thesystem works with the solar panel at low illumination conditions;

automatic search of the maximum efficiency point of the solar panels,when the irradiation conditions and the temperature conditions change,without using sensors or customised electric connections;

simple structure similar to a traditional motor electrical circuitdiagrarm not powered by solar panels;

the system works as a power supply “step-up”, carrying solar panelenergy on an external load comprising, for instance, the storage batteryof the vehicle, maximising the energy conversion efficiency through acustomised mathematical algorithm controlled by a microprocessor of acontrol unit;

possibility to supply a voltage stabilised at a low absolute value to anexternal load, when the system works with solar panels.

It is clear that several other changes, besides those mentioned above,can be made to the power supply system of the electronic switchingelectric motor in accordance with the present invention withoutdeparting from the principles of the inventive idea. In addition,different components and materials may be used according to the specifictechnical requirements.

What is claimed is:
 1. A power supply system of an electronicallycommutated DC permanent magnets electric motor (4, 52) suitable forinstallation inside air-conditioning devices for motor vehicles, thepower supply system including at least one solar panel (13) electricallywired to said electric motor (4, 52) and in turn to a plurality ofseries cells wired in such a way to collect available electrical energyat a substantially high voltage value and at a low current intensityvalue to allow a lower energy dissipation inside the power supplysystem, the electric motor (4, 52) comprising: a switch device (K1) thatswitches between at least two different positions corresponding to twooperating modes of the power system by means of a control provided by atleast one control unit (12) to connect alternatively the electric motorwith an energy storage battery (54) or with the solar panel (13); afirst capacitor (C2) connected between the switch device (K1) andground; a first coil (L1) connected on one end to the switch device (K1)and on the other end to a first transistor (TR1) which is connected toground via a shunt (SH1); a second coil (L3) connected on one end to theswitch device (K1) and on the other end to a second transistor (TR3)which is connected to ground via said shunt (SH1); a first diode (D4)whose anode is connected between the first coil (L1) and the firsttransistor (TR1); a second diode (D3) whose anode is connected betweenthe second coil (L3) and the second transistor (TR3) and whose cathodeis connected to the cathode of said first diode (D4); a second capacitor(C1) connected between the cathodes of said first and second diodes (D4,D3) and the ground via the shunt (SH1); a third coil (L2) and a thirdtransistor (TR2) connected in series across the capacitor (C1); a fourthcoil (L4) and a fourth transistor (TR4) connected in series across thesecond capacitor (C1); said first and second coils (L1, L3), said firstand second transistors (TR1, TR3), said first and second diodes (D4, D3)and said second capacitor (C1) forming a power source in the form of astep-up converter; and said third and fourth coils (L2, L4) and saidthird and fourth transistors (TR2, TR4) forming a first part (22) of ahigh voltage electronic circuit powered by said power source; theelectric motor (4, 52) being powered, alternatively, through an existingtraditional vehicle electric system or through the solar panel (13), andthe switching between said power sources being automatically managed bythe control unit (12) by commanding the switching element (K1) withoutany additional components interposed between any of said power sourcesand said motor in order to match different energetic characteristics ofany power source to the motor; the first part (22) of the high voltageelectronic circuit having, as its power source in a first system workingmode a current generator which comprises said storage battery (54), aplurality of coils (L1, L3) in switching mode, and a plurality of diodes(D3, D4), and in a second system working mode said solar panel connectedthrough at least one coil (L1, L3) and at least one capacitor (C1), insuch a way to power the first part (22).
 2. The power supply system asclaimed in claim 1, wherein said electronic control unit (12) comprisesat least one microprocessor which controls the operations of said firstpart (22) of the electronic circuit by driving with pulse-widthmodulation (PWM) said transistors (TR3, TR4), thus stabilising voltagein said second capacitor (C1) to a maximum efficiency value for thesolar panel (13).
 3. The power supply system as claimed in claim 2,wherein said microprocessor uses an application program whichperiodically executes small changes of a “duty cycle” around a workingpoint (G, H) of said solar panel (13) and verifies how such changesimpact a rotation speed of said motor (4), in order to take into accountefficiency changes of said solar panel (13) due to temperature and orconditions of irradiation changes.
 4. The power supply system as claimedin claim 3, wherein said switch K1) is used to protect said solar panel(13) from inverse voltage of said battery (54) when the system works inone of said two working modes.
 5. The power supply system as claimed inclaim 3, wherein said diodes (D3, D4) are used to protect the solarpanel (13) from inverse voltage caused by said motor (4) rotationbecause of aerodynamic or inertial effects when the system works in oneof said two working.
 6. The power supply system as claimed in claim 5,wherein said microprocessor controls a rotational positioning operationby activating a plurality of transistors (TR1, TR3) of a second part(111, 112) of the electronic circuit of said power supply system if saidmotor (4) does not move because it is positioned on a working pointwhich has a static torque equal to zero.
 7. The power supply system asclaimed in claim 6, wherein said first part (22) of the electroniccircuit is disabled while said transistors of said second part (111,112) of the electronic circuit are driven in parallel through apulse-width modulation control (PWM) by said electronic control unit(12).
 8. The power supply system as claimed in claim 7, wherein saidelectronic control unit (12) and said power supply source (14), togetherwith the first and second coils, the first and second diodes, and thefirst and second capacitors in said motor (4, 52) work as a “step-up”power supply system capable to power at least one external load (60),through an electromechanical or electronic switch device (1), controlledby said microprocessor of the electronic control unit (12).
 9. The powersupply system as claimed in claim 8, wherein said external load (60)comprises said motor vehicle storage battery (54).
 10. The power supplysystem as claimed in claim 8, wherein said microprocesser optimisesenergy conversion by measuring a voltage value at terminals of at leastone capacitor (C2) in the electronic circuit, putting said solar panel(13) to work at a maximum efficiency.
 11. The power supply system asclaimed in claim 8, wherein said motor (4, 52) supplies stabiliesvoltage to other external loads (60) by working as a parallel “shunt”linear regulator, said stabilised voltage being drained from at leastone capacitor (Cl) of the electronic power supply circuit of said motor(4, 52).
 12. The power supply system as claimed in claim 6, wherein saidsecond part (111, 112) of the electrontic circuit comprises a pluralityof electronic components (C1, C2, L1, L3) used for protection of themotor vehicle electric system from problems caused by operation of theelectric motor.